If your INR is too high, it might mean your blood clots too slowly, and there is a risk of bleeding. If your INR is too low, it might mean you have a risk of developing a blood clot. If you are not having warfarin treatment and your INR is higher than normal, you might need further tests. You can also read more about blood tests in general. Visit our Guide to blood testing to learn more about blood tests in general with information such as:.
Learn more here about the development and quality assurance of healthdirect content. Describes how the prothrombin time PT test is used, why the PT test is done, and what the results might mean. Read more on HealthEngine website.
Description of factors involved in coagulation of the blood, factors measured in the investigation of clotting disorders. The international normalised ratio INR is a laboratory measurement used to determine the effects of oral anticoagulants such as warfarin on the body's blood clotting.
Hypercoagulable disorders are a number of different conditions that lead to a predisposition to form blood clots. Explains how fibrinogen is used; when fibrinogen is used; what the results of fibrinogen might mean. Find out what the key considerations are when prescribing these drugs. Includes CPD activity for pharmacists. Read more on Australian Prescriber website. Healthdirect Australia is not responsible for the content and advertising on the external website you are now entering.
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How It Is Done The health professional drawing blood will: Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein. Clean the needle site with alcohol. Put the needle into the vein.
More than one needle stick may be needed. Attach a tube to the needle to fill it with blood. Remove the band from your arm when enough blood is collected. Put a gauze pad or cotton ball over the needle site as the needle is removed. Put pressure on the site and then put on a bandage. How It Feels The blood sample usually is taken from a vein in your arm. Risks There is very little chance of a problem from having a blood sample taken from a vein.
You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes. In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this. Results Prothrombin time PT is a blood test that measures how long it takes blood to clot. Normal The normal values listed here—called a reference range—are just a guide.
It can also mean a lack of vitamin K; liver disease, such as cirrhosis ; or that a liver injury has occurred. A longer-than-normal PT can also mean that you have disseminated intravascular coagulation DIC , a life-threatening condition in which your body uses up its clotting factors so quickly that the blood cannot clot and bleeding does not stop.
A longer-than-normal PT can be caused by treatment with blood-thinning medicines, such as warfarin Coumadin or, in rare cases, heparin. What Affects the Test Reasons you may not be able to have the test or why the results may not be helpful include: Taking medicines that can affect the action of warfarin and vitamin K. These include antibiotics, cimetidine, barbiturates, birth control pills, hormone therapy HT , and vitamin K supplements. Having severe diarrhea or vomiting that causes fluid loss and dehydration.
This may make the PT time longer. If diarrhea is caused by poor absorption of nutrients, vitamins, and minerals from the intestinal tract malabsorption syndrome , the PT may be longer because of a lack of vitamin K.
Eating foods that have a lot of vitamin K. These include many green vegetables such as kale, spinach, collard greens, broccoli, and Brussels sprouts. Drinking a lot of alcohol. Taking some herbal products or natural remedies.
What To Think About A PT is done at the same time of day each time so test results can check whether the right dose of warfarin is being used to prevent blood clots.
Another blood clotting test, called partial thromboplastin time PTT , measures other clotting factors. Partial thromboplastin time and prothrombin time are often done at the same time to check for bleeding problems.
To learn more, see the topic Partial Thromboplastin Time. Prothrombin levels are checked along with other liver tests, such as aspartate aminotransferase and alanine aminotransferase to check how the liver is working. If you were tested because you are taking warfarin, your results will probably be in the form of INR levels. INR levels are often used because they make it easier to compare results from different labs and different test methods.
If you are not taking warfarin, your results may be in the form of INR levels or the number of seconds it takes for your blood sample to clot prothrombin time. If you are not taking warfarin and your INR or prothrombin time results were not normal, it may mean one of the following conditions:. Learn more about laboratory tests, reference ranges, and understanding results. The information on this site should not be used as a substitute for professional medical care or advice.
Contact a health care provider if you have questions about your health. What is it used for? Warfarin is a blood-thinning medicine that's used to treat and prevent dangerous blood clots. Coumadin is a common brand name for warfarin. The test may be done on a blood sample from a vein or a fingertip.
For a blood sample from a vein: A health care professional will take a blood sample from a vein in your arm, using a small needle. For a blood sample from a fingertip: A fingertip test may be done in a provider's office or in your home. During this test, you or your provider will: Use a small needle to puncture your fingertip Collect a drop of blood and place it onto a test strip or other special instrument Place the instrument or test strip into a device that calculates the results.
At-home devices are small and lightweight. Will I need to do anything to prepare for the test? Are there any risks to the test? What do the results mean? If you are taking warfarin: INR levels that are too low may mean you are at risk for dangerous blood clots.
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